1. Field of the Invention
The present invention relates to optical systems and more particularly to targeting systems for military applications.
2. Brief Description of Related Art
In the prior art scene correlation is used to help solve the north keeping problem. That is, a way of finding north and keeping north for a period of time is needed so that the direction may be effective for targeting systems.
When using a prior art targeting system, the maintenance of north over time may become very difficult because most gyroscopes do not have the ability to retain north and they tend to have a high bias drift.
Typically, such gyroscopes may find north after about two minutes of integration time, but they may have a problem keeping north for more than two or three minutes. Consequently, after every two or three minutes the user may have to put the gyroscope back on the ground and find north yet again. As a result, the north vector looses accuracy over time. With the current state of the art, there may often be about 5 minutes before the user has to re-calibrate the north finder,